Web tension adjustment device and web winding device

ABSTRACT

A web tension adjustment device includes a pair of guide rollers and a dancer roller. The two guide rollers are spaced at least in a gravity direction and guide continuous paper in transfer. The dancer roller moves within a moving range along a guide shaft extending in a direction intersecting a rotation axis distance direction of the pair of guide rollers at an acute angle, rolls on the continuous paper transferred between the pair of guide rollers and gives tension to the continuous paper, the tension corresponding to an amount of moving from a position between the pair of guide rollers along the guide shaft.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit of priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-040999, filed on Mar. 7, 2018, the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a device to adjust tension in winding a web.

2. Description of the Related Art

Continuous paper fed from a paper feed roll to a printing apparatus is wound around a winding roll of a winding device after being printed at the printing apparatus. At that time, it is difficult to synchronize the speed of winding the continuous paper at the winding device with the speed of transferring the continuous paper at the printing apparatus. The winding device thus needs to give slack to the continuous paper to absorb changes in tension, due to the difference between the transfer speed and the winding speed of the continuous paper.

When the slack remains in the continuous paper wound around the winding roll, the continuous paper may have rumples or a tear, or unevenness may occur in winding the continuous paper. Accordingly, the winding device is provided with a tension adjustment mechanism for adjusting the tension of the continuous paper to wind the continuous paper around the winding roll without the slack.

The tension adjustment mechanism is arranged upstream of the winding roll of the winding device. A dancer roller mechanism of the tension adjustment mechanism includes a guide roller on an upstream side and a guide roller on a downstream side, and a dancer roller to be placed on continuous paper moving between the two guide rollers.

The dancer roller is configured to move up and down along a guide. The dancer roller pushes down the continuous paper, which moves between the guide roller on the upstream side and the guide roller on the downstream side, below the two guide rollers by its own weight. The amount of slack generated by pushing down the continuous paper is adjusted by balancing the weight of the dancer roller and the tension of the continuous paper (refer to Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-147740, for example).

Meanwhile, in the above-described dancer roller mechanism, when the paper feed roll for feeding continuous paper to the printing apparatus is replaced, a leading end of the continuous paper sent from the printing apparatus is to be hung across the two guide rollers and the dancer roller.

In this work, the dancer roller that has descended to a lower end of the guide by its own weight is moved up to a height of the guide rollers. The continuous paper is then inserted into gaps between the dancer roller and each of the two guide rollers to be wound around the lower half of the dancer roller. For this reason, the two guide rollers on the upstream side and the downstream side are spaced in a horizontal direction in some degree from the dancer roller that is moved to the height of the guide rollers. This arrangement prevents the dancer roller moved to the height of the guide rollers from coming in contact with the two guide rollers. Moreover, this ensures spaces between the dancer roller and each of the two guide rollers that are necessary for the work of winding the continuous paper around the dancer roller moved to the height of the guide rollers.

Instead of that, the winding device that houses the dancer roller mechanism needs a space for arranging the two guide rollers on the upstream side and the downstream side in the horizontal direction therein. The space leads to an increase in the size of the winding device in the horizontal direction. In the case of shortening the distance between the two guide rollers on the upstream side and the downstream side for preventing the increase in the size of the winding device, it sacrifices the ease of work of hanging across the continuous paper in replacement of the paper feed roll.

Such problems widely occur not only in winding continuous paper used for printing on the printing apparatus but also in winding a long web around the winding roll.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a web tension adjustment device and a web winding device suitable to achieve both an ease of work of hanging a web across a dancer roller and prevention of an increase in the size of the device.

According to a first aspect of the present invention, there is provided a web tension adjustment device including a pair of guide rollers spaced at least in a gravity direction and guiding a web in transfer, and a dancer roller that moves within a moving range along a guide extending in a direction intersecting a rotation axis distance direction of the pair of guide rollers at an acute angle, rolls on the web transferred between the pair of guide rollers and gives tension to the web, the tension corresponding to an amount of moving along the guide from a position between the pair of guide rollers.

According to the first aspect, it is possible to achieve both the ease of work of hanging a web across the dancer roller and the prevention of the increase in the size of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a schematic configuration of a printing system according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a detailed configuration of a winder shown in FIG. 1.

FIG. 3 is a diagram illustrating a detailed arrangement of a dancer roller and a pair of guide rollers in a tension adjustment device shown in FIG. 2.

FIG. 4 is a diagram illustrating a detailed arrangement of a dancer roller and a pair of guide rollers in the tension adjustment device according to a second exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating a detailed arrangement of a dancer roller and a pair of guide rollers in the tension adjustment device according to a third exemplary embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of a printing apparatus of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or similar reference symbol is attached to the same or similar part or structural element. It is noted that the drawings show schematic types and may be different from the actual apparatus. A relationship in size and a ratio in size may be different among the drawings.

The below-described exemplary embodiments present examples of an apparatus and the like for realizing the technical concept of the present invention. The technical concept of the present invention regarding an arrangement and the like of each structural component is not limited to these embodiments. Various modifications can be made in the technical concept of the present invention within the scope of claims.

First Embodiment

FIG. 1 is a diagram illustrating a schematic configuration of a printing system according to a first exemplary embodiment. The printing system shown in FIG. 1 includes a line-type inkjet recording machine 1 (hereinafter abbreviated as inkjet recording machine) and a winder 8.

The inkjet recording machine 1 includes a sending unit 2, an under-head transfer unit 3, and a printing unit 4.

The sending unit 2 includes paper feed rollers 2 a, and a tension adjustment device 2 b. The paper feed rollers 2 a send continuous paper 7, which is unwound from a paper feed roll 6 of a roll paper housing unit 5, to the under-head transfer unit 3.

The tension adjustment device 2 b is provided between the paper feed roll 6 and the paper feed rollers 2 a and includes a pair of guide rollers 2 c, 2 d, and a dancer roller 2 e.

The two guide rollers 2 c, 2 d are spaced in a horizontal direction. A distance between the guide rollers 2 c, 2 d is greater than the diameter of the dancer roller 2 e. The guide rollers 2 c, 2 d guide the continuous paper 7, which is transferred from the paper feed roll 6 to the paper feed rollers 2 a.

The dancer roller 2 e pushes down the continuous paper 7 between the guide rollers 2 c, 2 d by its own weight in a gravity direction to adjust the tension of the continuous paper 7. This tension adjustment enables the dancer roller 2 e to take up slack of the continuous paper 7 unwound from the paper feed roll 6.

The sending unit 2 may be separated from the inkjet recording machine 1 and configured as an independent paper feed device for the continuous paper 7.

The under-head transfer unit 3 transfers the continuous paper 7 sent from the sending unit 2 using drive rollers 3 a to a downstream side of the printing unit 4.

The printing unit 4 includes four head units 21, 22, 23, 24 of the colors of C (cyan), K (black), M (magenta) and Y (yellow), and a line sensor 26. The four head units 21, 22, 23, 24 are held by a head holder 25.

The head units 21, 22, 23, 24 are arranged to face the under-head transfer unit 3. The head units 21, 22, 23, 24 are line heads, each having a width wider than a recording region width of the continuous paper 7 in a main scanning direction (a back and front direction of the paper of FIG. 1) orthogonal to a transfer direction of the continuous paper 7.

Each of the head units 21, 22, 23, 24 discharges a drop of ink from a nozzle (illustration omitted) on a surface facing the under-head transfer unit 3 toward the continuous paper 7, which is transferred by the under-head transfer unit 3, according to a pattern corresponding to an image. The image is thus continuously printed on the continuous paper 7 in units of page.

The line sensor 26 reads an image that is printed on the continuous paper 7 with the colors of ink C, K, M, Y discharged from the nozzles of the head units 21, 22, 23, 24. The line sensor 26 is arranged in front of the winder 8 on a transfer route of the continuous paper 7.

The winder 8 receives the continuous paper 7, which has an image printed thereon by the printing unit 4 and is sent through a paper discharge aperture 1 a of the inkjet recording machine 1, through a receiving aperture 8 c formed on a side 8 b of a housing 8 a. The winder 8 then winds the continuous paper 7 around a winding roll 9.

It is difficult here to synchronize the speed of transferring the continuous paper 7 by the under-head transfer unit 3 of the inkjet recording machine 1 with the speed of winding the continuous paper 7 around the winding roll 9. The continuous paper 7, which is to be wound around the winding roll 9, thus needs to have slack to absorb changes in tension due to the difference in the two speeds.

However, when the slack remains in the continuous paper 7 wound around the winding roll 9, the continuous paper 7 may have rumples or a tear, or the winding roll 9 may have unevenness in winding the continuous paper 7. Upon this, the winder 8 has two configurations for winding the continuous paper 7 around the winding roll 9 without slack. One configuration is a tension adjustment device 10.

The tension adjustment device 10 is arranged in the housing 8 a of the winder 8 near the receiving aperture 8 c. The tension adjustment device 10 includes a pair of guide rollers 11, 12, and a dancer roller 13.

The pair of guide rollers 11, 12 guides the continuous paper 7, which is transferred through the receiving aperture 8 c to the winding roll 9. The dancer roller 13 pushes down the continuous paper 7 between the guide rollers 11, 12 by its own weight in the gravity direction to give tension to the continuous paper 7 in a direction to return to the receiving aperture 8 c.

The tension adjustment device 10 having such a configuration always gives constant tension to the continuous paper 7 in the direction to return to the receiving aperture 8 c without regard to presence or absence of the synchronization of the transfer speed with the winding speed of the continuous paper 7.

The other configuration provided on the winder 8 to wind the continuous paper 7 around the winding roll 9 without slack is a brake unit 14 illustrated in FIG. 2.

The brake unit 14 is spaced in the horizontal direction from the guide roller 12, which is arranged on a downstream side of the dancer roller 13 in the transfer direction of the continuous paper 7. The brake unit 14 includes a pair of guide rollers 14 a, 14 b, and a brake roller 14 c around which the continuous paper 7 between the guide rollers 14, 14 b is to be wound.

The pair of guide rollers 14 a, 14 b guides the continuous paper 7, which has passed the tension adjustment device 10. The brake roller 14 c applies a brake on the continuous paper 7, which is transferred from the tension adjustment device 10 to the winding roll 9. For the brake roller 14 c, for example, a powder brake may be used, which applies a brake by an electromagnetic clutch using magnetic iron powder.

The brake unit 14 having such a configuration applies a brake on the continuous paper 7, which has passed the tension adjustment device 10, to give tension to the continuous paper 7 in a direction sent to the winding roll 9.

Braking power of the brake unit 14 is defined by a speed of winding the continuous paper 7 by the winding roll 9. That is, the amount of tension given to the continuous paper 7 by the braking power of the brake unit 14 corresponds to the speed of winding the continuous paper 7 by the winding roll 9.

Accordingly, the continuous paper 7 is wound around the winding roll 9 without slack owing to the tension given to the continuous paper 7 by the tension adjustment device 10 in the direction to return to the receiving aperture 8 c in a constant amount, and the tension given to the continuous paper 7 by the brake unit 14 in the direction sent to the winding roll 9 in an amount corresponding to the speed of winding the continuous paper 7 around the winding roll 9.

The winding roll 9 is rotated by rotatory power of a winding motor 15 decelerated by a deceleration mechanism 16. A rotatory speed of the winding motor 15 is adjusted (decelerated) according to a change (increase) in a winding width of the continuous paper 7 wound around the winding roll 9. The rotatory power decelerated by the deceleration mechanism 16 and given to the winding roll 9 by the winding motor 15 is set higher than the braking power of the brake roller 14 c.

Meanwhile, a tension adjustment device using a conventional dancer roller has a configuration such as the tension adjustment device 2 b of the sending unit 2 shown in FIG. 1, where the dancer roller 2 e pushes down the continuous paper 7 between the guide rollers 2 c, 2 d spaced in the horizontal direction by its own weight. The dancer roller 2 e is configured to move up and down along the gravity direction to push down the continuous paper 7 efficiently by its own weight.

When the continuous paper 7 is hung across the tension adjustment device 2 b in replacement of the paper feed roll 6 or the like, the dancer roller 2 e is moved up to a height of the guide rollers 2 c, 2 d such that the continuous paper 7 inserted between the guide rollers 2 c, 2 d reaches the dancer roller 2 e. As a subsequent work, the continuous paper 7 is inserted into a space between the dancer roller 2 e and the guide roller 2 c and a space between the dancer roller 2 e and the guide roller 2 d to be wound around the lower half of the dancer roller 2 e.

To perform the work of winding the continuous paper 7 around the dancer roller 2 e by inserting the continuous paper 7 into the space between the dancer roller 2 e and the guide roller 2 c and the space between the dancer roller 2 e and the guide roller 2 d, it is necessary to maintain spaces required for the work. The tension adjustment device 2 b having the conventional configuration thus requires spacing the two guide rollers 2 c, 2 d to a certain extent in the horizontal direction to maintain spaces between the dancer roller 2 e and each of the guide rollers 2 c, 2 d. The arrangement of spacing the two guide rollers 2 c, 2 d in the horizontal direction however cannot avoid the increase in the size of the device in the horizontal direction.

Accordingly, the tension adjustment device 10 of the winder 8 of the present exemplary embodiment has a configuration different from the conventional configuration of the tension adjustment device 2 b. The configuration of the tension adjustment device 10 will be described below with reference to FIG. 3, which illustrates a detailed configuration of the tension adjustment device 10.

As shown in FIG. 3, the tension adjustment device 10 of the present exemplary embodiment is arranged in the housing 8 a of the winder 8 near the receiving aperture 8 c formed on the side 8 b. The tension adjustment device 10 differs from the tension adjustment device 2 b having the conventional configuration in spacing the pair of guide rollers 11, 12 not in the horizontal direction but in the gravity direction. A straight line C connecting a rotation axis of the guide roller 11 with a rotation axis of the guide roller 12 thus extends in the gravity direction.

The guide roller 11, which is one of the pair of guide rollers 11, 12 arranged on the upstream side of the dancer roller 13 in the transfer direction of the continuous paper 7, is arranged below the guide roller 12 in the gravity direction, the guide roller 12 being the other of the pair of guide rollers 11, 12 arranged on the downstream side of the dancer roller 13 in the transfer direction of the continuous paper 7.

The dancer roller 13 is rotatably supported on a carriage 13 a, which moves along a guide shaft G. The guide shaft G extends in a direction inclined at an angle of θ to the gravity direction (direction of the straight line C). The guide shaft G having the extending direction inclined to the gravity direction shortens a moving distance of the dancer roller 13 in the gravity direction and reduces a space occupied by the tension adjustment device 10 in the gravity direction.

In the tension adjustment device 10 of the present exemplary embodiment, a rotation axis distance L between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side is defined as a distance that satisfies the following formula:

L=(r1+r2+d3+a)/sin θ.

In the above formula, “r1” is a radius of the guide roller 11 on the upstream side, “r2” is a radius of the guide roller 12 on the downstream side, and “d3” is a diameter of the dancer roller 13. Moreover, “a” is a minimum clearance between the guide roller 11 on the upstream side, which is one of the pair of guide rollers 11, 12 arranged below in the gravity direction, and the dancer roller 13 when the dancer roller 13 makes the closest approach to the guide roller 11.

Moreover, “θ” is the angle formed by a rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (=gravity direction) and the extending direction of the guide shaft G. The reason why the rotation axis distance L between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side is defined as a distance that satisfies the above formula will be described below.

In the tension adjustment device 10 of the present exemplary embodiment, when the dancer roller 13 moves along the guide shaft G within a moving range toward an upper limit position, the dancer roller 13 passes by the guide roller 11 on the upstream side, which is arranged below in the gravity direction, from down to up.

This requires a clearance between the guide roller 11 on the upstream side and the dancer roller 13 when the dancer roller 13 passes by the guide roller 11 on the upstream side to make the closest approach to the guide roller 11.

Without this clearance, the dancer roller 13 comes in contact with the continuous paper 7, which is wound around the guide roller 11 on the upstream side, when the dancer roller 13 passes by the guide roller 11 on the upstream side. This contact may cause rumples or a tear on the continuous paper 7, or unevenness in winding the continuous paper 7 around the winding roll 9. Provision of the clearance between the guide roller 11 on the upstream side and the dancer roller 13 is thus indispensable.

When the clearance is provided between the guide roller 11 on the upstream side and the dancer roller 13, the amount of tension given to the continuous paper 7 between the dancer roller 13 and the guide roller 11 on the upstream side however changes according to a position to which the dancer roller 13 moves. To minimize the degree of change of the tension given to the continuous paper 7, it is preferable to minimize the clearance provided between the guide roller 11 on the upstream side and the dancer roller 13.

Moreover, in the tension adjustment device 10 of the present exemplary embodiment, the dancer roller 13 is required to be in contact with the continuous paper 7 to adjust the tension given to the continuous paper 7 between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side.

Here, the guide roller 11 on the upstream side and the guide roller 12 on the downstream side are spaced in the gravity direction. The dancer roller 13 in contact with the continuous paper 7 between the two guide rollers 11, 12 thus does not go over the guide roller 12 on the downstream side, which is one of the two guide rollers 11, 12 arranged above in the gravity direction.

Accordingly, when moving toward the upper limit position within the moving range, the dancer roller 13 in contact with the continuous paper 7 does not pass by the guide roller 12 on the downstream side. This requires no clearance between the guide roller 12 on the downstream side and the dancer roller 13 to prevent the contact of the dancer roller 13 with the guide roller 12.

In the tension adjustment device 10 of the present exemplary embodiment, the rotation axis distance L between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side is thus defined to satisfy the above-described formula:

L=(r1+r2+d3+a)/sin θ.

This prevents the dancer roller 13 in motion from coming in contact with the guide roller 11 on the upstream side, and minimizes the degree of change of the tension given to the continuous paper 7 according to the moving position of the dancer roller 13.

In the tension adjustment device 10 of the present exemplary embodiment, the guide roller 11 on the upstream side and the guide roller 12 on the downstream side are arranged with no space therebetween in the horizontal direction. This prevents the increase in the size of the winder 8 in the horizontal direction to the maximum.

Moreover, in the tension adjustment device 10 of the present exemplary embodiment, the angle θ between the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) and the extending direction of the guide shaft G of the dancer roller 13 is set to 20 degrees or greater. Furthermore, in the tension adjustment device 10 of the present exemplary embodiment, an angle θ1 (=angle θ) between the gravity direction (=rotation axis distance direction between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C)) and the extending direction of the guide shaft G of the dancer roller 13 is set to 30 degrees or less.

Supposing that the angle θ between the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) and the extending direction of the guide shaft G is less than 20 degrees, the dancer roller 13 in motion has a possibility of coming in contact with the guide roller 11 on the upstream side. This is because a moving distance of the dancer roller 13 in the horizontal direction in comparison with a moving distance of the dancer roller 13 along the guide shaft G becomes too short.

To prevent the dancer roller 13 in motion from coming in contact with the guide roller 11 on the upstream side, it is effective to maintain the rotation axis of the guide roller 11 on the upstream side and the rotation axis of the guide roller 12 on the downstream side widely apart from each other in the gravity direction. This enables the dancer roller 13 to move in the horizontal direction for a distance not to come in contact with the guide roller 11 on the upstream side before the dancer roller 13 in motion passes by the guide roller 11 on the upstream side.

Setting the guide roller 11 on the upstream side and the guide roller 12 on the downstream side widely apart from each other in the gravity direction however requires enlarging the space of arranging the pair of guide rollers 11,12 in the gravity direction. This cannot prevent the increase in the size of the winder 8 sufficiently.

Moreover, supposing that the angle θ1 (=angle θ) between the gravity direction (=rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C)) and the extending direction of the guide shaft G is over 30 degrees, the tension adjustment of the continuous paper 7 by the dancer roller 13 cannot be performed sufficiently. This is because mechanical loss (a loss in lubrication in moving of the dancer roller 13 and a loss in the amount of load applied to the continuous paper 7 by the dancer roller 13) increases due to the resistance of slidable movement between the dancer roller 13 and the guide shaft G.

Moreover, in addition to the space for the dancer roller 13 to move in the gravity direction necessary for pushing down the continuous paper 7 by its own weight, a space for the dancer roller 13 to move in the horizontal direction necessary for moving along the guide shaft G increases.

It is thus necessary to maintain the moving space for the dancer roller 13 wide in the horizontal direction in the housing 8 a of the winder 8, so that the increase in the size of the winder is not prevented sufficiently. Moreover, in a case of preventing contact with the existing peripheral parts in the housing 8 a, it is further difficult to prevent the increase in the size of the winder 8.

For these reasons, the angle θ between the rotation axis distance direction of the pair of guide rollers 11, 12 (direction of the straight line C) and the extending direction of the guide shaft G is set to 20 degrees or greater, and the angle θ1 (=angle θ) between the gravity direction (=direction of the straight line C) and the extending direction of the guide shaft G is set to 30 degrees or less. This achieves both the ease of work of winding the continuous paper 7 around the dancer roller 13 and the prevention of an increase in the size of the winder 8 without losing the tension adjustment function for the continuous paper 7 by the dancer roller 13.

In the tension adjustment device 10 of the present exemplary embodiment having such a configuration, the continuous paper 7 received through the receiving aperture 8 c is guided by the guide roller 11 on the upstream side to be sent to a lower part of the housing 8 a and is folded up at the dancer roller 13 toward an upper part of the housing 8 a. The folded up continuous paper 7 is guided by the guide roller 12 on the downstream side to be transferred to the brake unit 14, which is adjacent to the guide roller 12 on the downstream side in the horizontal direction.

The dancer roller 13 then pushes down the continuous paper 7 between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side in the gravity direction by its own weight. At this time, the dancer roller 13 pushes down the continuous paper 7 to a position where the load applied to the continuous paper 7 by its own weight is balanced with the tension of the continuous paper 7 and thus adjusts the tension given to the continuous paper 7 to a constant amount.

The dancer roller 13 pushing down the continuous paper 7 by its own weight moves within an area (control area) described as “tension adjustment control range” in FIG. 3, which is below the guide roller 11 on the upstream side.

When new continuous paper 7 is transferred from the inkjet recording machine 1 to the winder 8 through the receiving aperture 8 c, the dancer roller 13 is moved together with the carriage 13 a to an upper limit of “dancer roller moving range” (work position) described in FIG. 3 by a power source (illustration omitted).

In the present exemplary embodiment, at the upper limit of the dancer roller moving range, the rotation axis of the dancer roller 13 is on the straight line C, which connects the rotation axis of the guide roller 11 on the upstream side with the rotation axis of the guide roller 12 on the downstream side. However, the position of the rotation axis of the dancer roller 13 at the upper limit of the dancer roller moving range may be the inside of the housing 8 a (right side in FIG. 3) or to the outside of the housing 8 a (left side in FIG. 3) with respect to the straight line C.

That is, the position of the dancer roller 13 at the upper limit of the dancer roller moving range may be a position closer to the guide roller 11 on the upstream side and the guide roller 12 on the downstream side than a position at which the dancer roller 13 pushes down the continuous paper 7 by its own weight (area of the tension adjustment control range in FIG. 3). A leading end of new continuous paper 7 is wound around the lower half of the dancer roller 13 more easily at the upper limit position in the dancer roller moving range than at a position within the tension adjustment control range.

Here, the tension adjustment device 10 of the present exemplary embodiment maintains a distance that is wider than that in the conventional tension adjustment device having a pair of guide rollers spaced in the horizontal direction, as the rotation axis distance L between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side.

This ensures spaces between the dancer roller 13 and each of the two guide rollers 11, 12 that are wider than that in the conventional tension adjustment device having the pair of guide rollers spaced in the horizontal direction, while the dancer roller 13 moves to the upper limit position between the two guide rollers 11, 12.

Accordingly, when the new continuous paper 7 is transferred to the winder 8, the leading end of the new continuous paper 7 is easily inserted into the spaces opened in the gravity direction between the dancer roller 13 at the upper limit position and each of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side and is easily wound around the lower half of the dancer roller 13.

Moreover, in the tension adjustment device 10 of the present exemplary embodiment, the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) is made to correspond to the gravity direction. The rotation axis distance L between the guide roller 11 on the upstream side and the guide roller 12 on the downstream side is thus zero in the horizontal direction. Accordingly, the space of arranging the pair of guide rollers 11, 12 is made smaller in the horizontal direction than that in the conventional tension adjustment device having the pair of guide rollers spaced in the horizontal direction.

Accordingly, achievement of the ease of work of winding the leading end of the new continuous paper 7 around the dancer roller 13 by enlarging the spaces between the dancer roller 13 and each of the two guide rollers 11, 12, leads to prevent the increase in the size of the housing 8 a of the winder 8 in the horizontal direction.

A direction in which the dancer roller 13 moves along the guide shaft G includes a component of the gravity direction, so that downward moving of the dancer roller 13 in the gravity direction by its own weight within the moving range is not disturbed by contact of the carriage 13 a supporting the dancer roller 13 with the guide shaft G.

Consequently, when the dancer roller 13 moves in a direction inclined to the gravity direction, the configuration is not lost and is maintained in which the dancer roller 13 rolls on the continuous paper 7 between the two guide rollers 11, 12, pushes down the continuous paper 7 in the gravity direction by its own weight and gives tension corresponding to the amount of moving along the guide shaft G to the continuous paper 7. The above-described tension adjustment device 10 of the exemplary embodiment achieves both the ease of work of winding the continuous paper 7 around the lower half of the dancer roller 13 and the prevention of the increase in the size of the winder 8.

In the above-described tension adjustment device 10 of the exemplary embodiment, the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) is made to correspond to the gravity direction. The rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side however may be inclined to the gravity direction.

Second Embodiment

In the tension adjustment device 10 according to a second exemplary embodiment shown in FIG. 4, the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) is inclined to the gravity direction (direction of a straight line V) to a side opposite to the extending direction of the guide shaft G of the dancer roller 13.

Also, in this case, the angle θ between the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) and the extending direction of the guide shaft G of the dancer roller 13 is set to 20 degrees or greater. Moreover, the angle θ1 between the gravity direction (direction of the straight line V) and the extending direction of the guide shaft G is set to 30 degrees or less.

Third Embodiment

In the tension adjustment device 10 according to the first and the second exemplary embodiments, the extending direction of the guide shaft G is inclined to the gravity direction. However, as in the tension adjustment device 10 according to a third exemplary embodiment shown in FIG. 5, the extending direction of the guide shaft G may be made to correspond to the gravity direction (direction of the straight line V).

In this case, the angle θ between the rotation axis distance direction of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side (direction of the straight line C) and the extending direction of the guide shaft G of the dancer roller 13 is set to 20 degrees or greater. As the extending direction of the guide shaft G is made to correspond to the gravity direction (direction of the straight line V), there is no limitation for the range of the angle between the gravity direction (direction of the straight line V) and the extending direction of the guide shaft G.

OTHER EMBODIMENTS

In the tension adjustment device 10 according to each of the above-described exemplary embodiments, the rotation axis distance L of the guide roller 11 on the upstream side and the guide roller 12 on the downstream side is defined to satisfy the formula:

L=(r1+r2+d3+a)/sin θ.

The rotation axis distance L however may be set to a value that does not satisfy the above formula.

In the above-described exemplary embodiments, the present invention is applied to the tension adjustment device 10 of the winder 8 to wind the continuous paper 7 on which an image is printed by the inkjet recording machine 1. It is however not limited to this application. For example, the present invention is applicable to a winding device that winds a long web around a winding roll, and a tension adjustment device that rolls on a web transferred between a pair of guide rollers to give tension corresponding to the amount of moving along a guide from a position between the pair of guide rollers.

The web tension adjustment device of the first exemplary embodiment of the present invention includes a pair of guide rollers spaced at least in a gravity direction and guiding a web in transfer, and a dancer roller that moves within a moving range along a guide extending in a direction intersecting a rotation axis distance direction of the pair of guide rollers at an acute angle, rolls on the web transferred between the pair of guide rollers and gives tension to the web, the tension corresponding to an amount of moving along the guide from a position between the pair of guide rollers.

According to the web tension adjustment device of a first aspect, for the pair of guide rollers, one guide roller arranged on the upstream side of the dancer roller in the transfer direction of the web, and the other guide roller arranged on the downstream side of the dancer roller in the transfer direction of the web are spaced at least in the gravity direction.

Even if the space same as that in the conventional configuration with the pair of guide rollers spaced in the horizontal direction is maintained for the rotation axis distance of the two guide rollers, the space between the two guide rollers in the horizontal direction is made smaller for the space maintained in the gravity direction.

Accordingly, while the dancer roller moves between the pair of guide rollers along the guide, it is possible to ensure the spaces between the dancer roller and each of the guide rollers same as that in the conventional configuration.

In addition, the space of arranging the pair of guide rollers is made smaller in the horizontal direction than that in the conventional configuration with the pair of guide rollers spaced in the horizontal direction. This achieves the prevention of the increase in the size of the device.

Moreover, the moving direction of the dancer roller along the guide, which intersects at an acute angle with the rotation axis distance direction of the pair of guide rollers spaced at least in the gravity direction, includes a component of the gravity direction. The downward moving of the dancer roller in the gravity direction by its own weight within the moving range is thus not disturbed by the contact of the dancer roller with the guide.

Consequently, the configuration is not lost and is maintained in which the dancer roller moving within the moving range rolls on the web between the pair of guide rollers, pushes down the web in the gravity direction by its own weight and gives tension corresponding to the amount of moving along of the guide to the web.

As described above, it is possible to achieve both the ease of work of hanging the web across the dancer roller and the prevention of the increase in the size of the device.

According to the web tension adjustment device of a second aspect of the present invention, the dancer roller gives tension to the web in the control area that is below the pair of guide rollers in the gravity direction within the moving range and moves upward within the moving range to the work position between the pair of guide rollers in the work of hanging across the web.

According to the web tension adjustment device of the second exemplary embodiment, in the work of hanging across the web, it is possible to move the dancer roller that is placed in the control area below the pair of guide rollers in the gravity direction to the work position between the pair of guide rollers and thus achieve the ease of work of hanging the web across the dancer roller through the spaces between the dancer roller and each of the guide rollers.

According to the web tension adjustment device of a third aspect of the present invention, the extending direction of the guide is a direction inclined at an angle of 20 degrees or greater to the rotation axis distance direction and at an angle of 30 degrees or less to the gravity direction.

In the web tension adjustment device of the first and the second aspect, when the inclination of the extending direction of the guide of the dancer roller to the rotation axis distance direction of the pair of guide rollers is less than 20 degrees, a moving distance of the dancer roller in the horizontal direction with respect to the moving distance of the dancer roller along the guide is too small to have a possibility that the dancer roller in motion comes in contact with the guide roller.

To prevent the dancer roller in motion from coming in contact with the guide roller, it is effective to set the rotation axes of the pair of guide rollers widely apart from each other in the gravity direction. This enables the dancer roller to move in the horizontal direction for a distance not to come in contact with the guide roller before the dancer roller passes by the guide roller.

Setting the pair of guide rollers widely apart in the gravity direction however requires enlarging the space of arranging the pair of guide rollers in the gravity direction and cannot prevent the increase in the size of the device sufficiently.

Moreover, when the angle between the gravity direction and the extending direction of the guide of the dancer roller goes over 30 degrees, the mechanical loss (a loss in lubrication in moving of the dancer roller and a loss in the amount of load applied to the web by the dancer roller) increase due to the resistance of slidable movement between the dancer roller and the guide. Accordingly, the tension adjustment of the web by the dancer roller is not performed sufficiently.

Furthermore, in addition to the moving space of the dancer roller required in the gravity direction to push down the web by its own weight of the dancer roller, the moving space of the dancer roller required in the horizontal direction to move the dancer roller along the guide increases.

It is thus necessary to maintain the moving space for the dancer roller wide in the horizontal direction in the device, so that the increase in the size of the device is not prevented sufficiently. Moreover, in a case of preventing contact with the existing peripheral parts in the device, it is further difficult to prevent the increase in the size of the device.

For these reasons, in the web tension adjustment device of the third aspect, the angle between the rotation axis distance direction of the pair of guide rollers and the extending direction of the guide of the dancer roller is set to 20 degrees or greater, and the angle between the gravity direction and the extending direction of the guide of the dancer roller is set to 30 degrees or less. This achieves both the ease of work of hanging across the web and the prevention of the increase in the size of the device without losing the tension adjustment function for the web by the dancer roller.

According to the web tension adjustment device of a fourth aspect of the present invention, the pair of guide rollers and the dancer roller are arranged on the transfer route of the web, which is to be wound around the winding roll.

According to the web tension adjustment device of the fourth aspect, the tension given to the web is adjusted on the transfer route of the web, which is to be wound around the winding roll, and it is possible to achieve both the ease of work of hanging the web across the dancer roller and the prevention of an increase in the size of the device.

According to the web tension adjustment device of a fifth aspect of the present invention, the rotation axis distance L of the pair of guide rollers satisfies the formula:

L=(r1+r2+d3+a)/sin θ

where “r1” is a radius of the guide roller on the upstream side, which is one of the pair of guide rollers arranged upstream of the dancer roller in the transfer direction of the web, “r22 is a radius of the guide roller on the downstream side, which is the other of the pair of guide rollers arranged downstream of the dancer roller in the transfer direction of the web, “d32 is a diameter of the dancer roller, “a” is a minimum clearance between the guide roller and the dancer roller, the guide roller being one of the guide roller on the upstream side and the guide roller on the downstream side arranged below in the gravity direction, and “θ” is an angle between the rotation axis distance direction and the extending direction of the guide. In the web tension adjustment device of the first, the second, the third, or the fourth aspect when the dancer roller moves toward the upper limit position within the moving range in which the dancer roller passes between the guide roller on the upstream side and the guide roller on the downstream side, the dancer roller passes by the guide roller from down to up, the guide roller being one of the two guide rollers arranged below in the gravity direction.

This requires a clearance between the dancer roller and the below guide roller when the dancer roller passes by the below guide roller and the two rollers make the closest approach each other. Without this clearance, the dancer roller comes in contact with the web wound around the below guide roller when passing by the below guide roller.

When the clearance is provided between the below guide roller and the dancer roller, the amount of tension given to the web between the dancer roller and the below guide roller however changes according to the moving position of the dancer roller. To minimize the degree of change of the tension given to the web, it is preferable to minimize the clearance provided between the two rollers.

Moreover, in the web tension adjustment device of the first, the second, the third, or the fourth aspect, the dancer roller is required to be in contact with the web to adjust the tension given to the web between the guide roller on the upstream side and the guide roller on the downstream side.

Here, the guide roller on the upstream side and the guide roller on the downstream side are separated at least in the gravity direction. The dancer roller in contact with the web thus does not go over the guide roller that is one of the two guide rollers arranged above in the gravity direction.

When the dancer roller moves toward the upper limit position within the moving range in which the dancer roller passes between the guide roller on the upstream side and the guide roller on the downstream side, the dancer roller in contact with the web does not pass by the guide roller that is one of the two guide rollers arranged above in the gravity direction.

This requires no clearance between the dancer roller and the above guide roller to prevent the contact of the two rollers.

Then, the rotation axis distance between the guide roller on the upstream side and the guide roller on the downstream side is defined to satisfy the formula of the fifth aspect. This prevents the dancer roller in motion from coming in contact with the guide roller that is one of the two guide rollers arranged below in the gravity direction and minimizes the degree of change of the tension given to the web according to the moving position of the dancer roller.

As a modification of the first, the second, the third, the fourth, or the fifth aspect, the extending direction of the guide is set as a direction inclined to the gravity direction.

As another modification of the first, the second, the third, the fourth, or the fifth aspect, the pair of guide rollers is arranged to have the rotation axis distance direction corresponding to the gravity direction.

According to these modifications, the pair of guide rollers is arranged without a space therebetween in the horizontal direction. This maximizes the prevention of the increase in the size of the device.

The web tension adjustment device of a sixth aspect of the present invention includes the winder that winds the web, and the tension adjustment mechanism that adjusts tension given to the web, which is to be wound by the winder. For the tension adjustment mechanism, the web tension adjustment device of the first, the second, the third, the fourth, or the fifth aspect is used.

According to the sixth aspect, the web tension adjustment device of the first, the second, the third, the fourth, or the fifth aspect is used as the tension adjustment mechanism that adjusts the tension of the web, which is to be wound around the winder. It is thus possible to obtain the effects obtained by the web tension adjustment device of the first, the second, the third, the fourth, or the fifth aspect.

As a modification of the sixth aspect, a casing that has the receiving aperture for the web on the side thereof is further provided. The web tension adjustment device is provided within the casing. The pair of guide rollers of the web tension adjustment device is arranged along the side of the casing. 

What is claimed is:
 1. A web tension adjustment device, comprising: a pair of guide rollers spaced at least in a gravity direction and guiding a web in transfer; and a dancer roller that moves within a moving range along a guide extending in a direction intersecting a rotation axis distance direction of the pair of guide rollers at an acute angle, rolls on the web transferred between the pair of guide rollers and gives tension to the web, the tension corresponding to an amount of moving along the guide from a position between the pair of guide rollers.
 2. The web tension adjustment device according to claim 1, wherein the dancer roller gives the tension to the web in a control range that is positioned lower than the pair of guide rollers in the gravity direction within the moving range and moves upward within the moving range to a work position between the pair of guide rollers in a work of hanging across the web.
 3. The web tension adjustment device according to claim 1, wherein the extending direction of the guide is a direction inclined at an angle of 20 degrees or greater to the rotation axis distance direction and at an angle of 30 degrees or less to the gravity direction.
 4. The web tension adjustment device according to claim 1, wherein the pair of guide rollers and the dancer roller are arranged on a transfer route of the web to be wound around a winding roll.
 5. The web tension adjustment device according to claim 1, wherein a rotation axis distance L of the pair of guide rollers satisfies a formula: L=(r1+r2+d3+a)/sin θ where “r1” is a radius of a guide roller on an upstream side, the guide roller on the upstream side being one, arranged upstream of the dancer roller in a transfer direction of the web, of the pair of guide rollers, “r2” is a radius of a guide roller on a downstream side, the guide roller on the downstream side being the other, arranged downstream of the dancer roller in the transfer direction of the web, of the pair of guide rollers, “d3” is a diameter of the dancer roller, “a” is a minimum clearance between a guide roller and the dancer roller, the guide roller being one of the guide roller on the upstream side and the guide roller on the downstream side arranged below in the gravity direction, and “θ” is an angle between the rotation axis distance direction and the extending direction of the guide.
 6. A web winding device, comprising: a winder that winds a web; and a web tension adjustment device used for a tension adjustment mechanism that adjusts tension of the web to be wound by the winder, wherein the web tension adjustment device includes: a pair of guide rollers spaced at least in a gravity direction and guiding the web in transfer; and a dancer roller that moves within a moving range along a guide extending in a direction intersecting a rotation axis distance direction of the pair of guide rollers at an acute angle, rolls on the web transferred between the pair of guide rollers and gives tension to the web, the tension corresponding to an amount of moving along the guide from a position between the pair of guide rollers. 